The present invention relates to video cards and more particularly to a synchronous-signal polarity converter of a video card, which converts the polarity of synchronous signals provided from a video card in case of necessity, a monitor. Generally, the video cards are used in computers to display graphics etc. on a monitor. But, each polarity of synchronous signals of these video cards are different from each other according to makers. Thus, the user has to prepare either a monitor which is suitable to the polarity of synchronous signals provided from a video card or a video card which is suitable to the polarity of synchronous signals in a presently used monitor.
FIG. 1 is a conventional synchronous-signal generator of a video card. The graphic data provided from a graphic processor GP are transferred to a video random access memory (VRAM) or a dynamic random access memory (DRAM) for the storage of pixels according to the video data through a buffer BF. At this time, vertical synchronous signals (V-SYNC) and horizontal synchronous signals (H-SYNC) of a positive or negative polarity are respectively applied to exclusive OR gates EX-OR 1 and EX-OR 2 as shown in FIG. 1. Another terminals of the exclusive OR gates EX-OR 1 and EX-OR 2 are grounded. Thus, the exclusive OR gates EX-OR1 and EX-OR2 provide the vertical and horizontal synchronous signals respectively, without changing the polarity of the vertical and horizontal synchronous signals. However, the user must select a video card according to the synchronous-signal polarity of a presently used monitor, since the polarity of the vertical and horizontal synchronous signals were already determined according to the video cards.